Apparatus and Method for Compressing a Cryogenic Media

ABSTRACT

An apparatus and method for compressing a cryogenic media is disclosed. The apparatus includes a compressor compartment surrounded by a cylinder wall, a compressor piston being moved linearly in the compartment, an intake valve, and a compression valve, both valves being arranged in the area of the lower end position of the compressor piston. The compression valve is arranged laterally on the cylinder wall in the area of the lower end position of the compressor piston, and the head of the compressor piston has a conical shape.

This application claims the priority of International Application No. PCT/EP2006/004624, filed May 16, 2006, and German Patent Document No. 10 2005 024 888.8, filed May 31, 2005, the disclosures of which are expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a compressor, in particular a compressor for cryogenic media, preferably for liquid hydrogen, having a compressor compartment surrounded by a cylinder wall in which a compressor piston is moved linearly, an intake valve and a compression valve, both valves being arranged in the area of the lower end position of the compressor piston.

The term “cryogenic media” is understood below to refer to so-called deep cold fluids, in particular liquid hydrogen, liquefied natural gas, liquid nitrogen, liquid oxygen and other liquefied gases.

Compressors of this type are sufficiently well known from the state of the art. They all have in common the fact that the medium to be compressed is fed through a spring-loaded valve into a compressor compartment, where it is compressed and then removed from the compressor compartment via a spring-loaded compression valve.

FIG. 1 shows a lateral schematic sectional diagram of a generic compressor design belonging to the state of the art.

A compressor piston K′ is moved linearly back and forth and/or up and down within a compressor compartment R surrounded by a cylinder wall Z. The two reversing points of the compressor piston K′ are referred to below as the upper and lower end positions of the compressor piston K′.

An intake valve S and a compression valve D′ are arranged on the lower side of the cylinder compartment. During the intake stroke—during which the compressor piston K′ moves from its lower end position into its upper end position, i.e., from bottom to top in the present case—the liquid medium to be compressed enters the compressor compartment R through the intake valve S. During the following compression stroke—the compressor piston K′ moves from its upper end position back into its lower end position, which is shown in FIG. 1—the compressed medium is forced out of the compressor compartment R through the compression valve D′.

In liquid compression of a liquid cryogenic medium in particular, a gas phase G necessarily develops during compression. If the gas phase remains in the unavoidable dead space of the compressor compartment R after the compression stroke, then the gaseous medium will decompress inside the compressor compartment R during the following intake stroke. During this decompression, no new cryogenic medium can be drawn into the compressor compartment R through the intake valve S. Therefore, this results in a significant reduction in the delivery capacity of the compressor.

If the dead space were filled exclusively with liquid at the end of the compression stroke, then the unwanted decompression of the gaseous medium described above could be prevented. With all known compressor designs, the intake valve S and the compression valve D′ sit at the lower end of the cylinder housing Z. As a result, the liquid phase F is forced out of the compressor compartment R first by the compressor piston K′ through the compression valve D′ while a gas phase G necessarily remains in the remaining dead space.

It is fundamentally impossible to continue the movement of the compressor piston K′ as far as the bottom of the cylinder space Z and thereby reduce or “eliminate” the dead space. This is due to the optimization of the dead space of compressors. A certain dead space cannot be prevented due to the longitudinal expansion in cooling. If no dead space were provided, the valves could not even be integrated into the compressor.

However, the gas phase G, which necessarily remains in the dead space, expands after compression and thereby reduces the influx of “fresh” liquid to be compressed.

The object of the present invention is to provide a generic compressor, in particular a generic compressor for cryogenic media, with which the aforementioned disadvantages can be avoided.

To achieve this object, a generic compressor is provided and is characterized in that the compression valve is arranged laterally on the cylinder wall in the area of the lower end position of the compressor piston, and the head of the compressor piston has a conical shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a lateral schematic sectional diagram of a generic compressor design belonging to the state of the art.

FIG. 2 shows a lateral schematic sectional diagram through one possible embodiment of the inventive compressor.

DETAILED DESCRIPTION OF THE DRAWINGS

The inventive compressor and other embodiments of same will now be explained in greater detail on the basis of the exemplary embodiment shown in FIG. 2.

FIG. 2 also shows—as already shown in FIG. 1—a lateral schematic sectional diagram through one possible embodiment of the inventive compressor.

With the compressor piston K shown in FIG. 2, its head has a conical shape (area x). In addition, the compression valve D is now arranged laterally on the cylinder wall Z in the area of the lower end position of the compressor piston K.

If the compressor piston K is now at the end of the compression stroke in its lower end position (as illustrated in FIG. 2), the remaining dead space G, which is filled with gaseous medium, is now much smaller than that in the compressor design illustrated in FIG. 1. In addition, because of the conical shape x of the compressor piston K, there is a “connection” to the compression valve D, so that compressed cryogenic medium can be discharged from the dead space through the compression valve D.

At the end of the compression stroke, however, a liquid phase F remains and cannot be completely discharged through the compression valve D by the compressor piston K moving into the lower end position.

As a result, at the start of the following intake stroke, there is a definitely reduced quantity of gas to be decompressed-if the remaining dead space is not completely filled with liquid-before liquid cryogenic medium can again be drawn in through the intake valve S.

In conclusion, it should be pointed out that in FIGS. 1 and 2 the sealing means optionally to be provided between the compressor piston K′ and/or K and the cylinder wall Z are not shown for the sake of simplicity.

The inventive compressor described above achieves the result that the amount of gas present in the compressor compartment at the end of the compression stroke is eliminated or at least largely reduced. This in turn results in a higher delivery capacity in comparison with known compressor designs. A reduction in the specific compressor output based on the quantity of medium compressed, i.e., conveyed, can therefore be achieved.

The advantages associated with the inventive compressor are achieved by a slightly more complex compressor design in comparison with the state of the art, but the resulting increase in cost is more than compensated by the advantages achieved with this design. 

1. (canceled)
 2. A compressor for cryogenic media, comprising a compressor compartment surrounded by a cylinder wall in which a compressor piston moves linearly, an intake valve, and a compression valve, wherein both valves are arranged in an area of a lower end position of the compressor piston, and wherein the compression valve is arranged laterally on the cylinder wall in the area of the lower end position of the compressor piston and a head of the compressor piston has a conical shape.
 3. An apparatus for compressing a cryogenic media, comprising: a cylinder defined by a cylinder side wall and a cylinder bottom wall; a piston linearly moveable within the cylinder; an intake valve disposed in the bottom wall of the cylinder; and a compression valve disposed in the cylinder side wall.
 4. The apparatus according to claim 3, wherein the compression valve is disposed in the cylinder side wall at a lowest end of a stroke by the piston in the cylinder.
 5. The apparatus according to claim 3, wherein a head of the piston has a conical portion.
 6. The apparatus according to claim 5, wherein when the piston is at a lowest end of a stroke by the piston, the conical portion of the piston head is located adjacent to the compression valve.
 7. A method for compressing a cryogenic media in a cylinder defined by a cylinder side wall and a cylinder bottom wall, comprising the steps of: providing the cryogenic media to the cylinder through an intake valve disposed in the bottom wall of the cylinder; compressing the cryogenic media in the cylinder by moving a piston within the cylinder from a top-most position in the cylinder to a lowest-most position in the cylinder; and forcing the compressed cryogenic media out of the cylinder through a compression valve disposed in the cylinder side wall.
 8. The method according to claim 7, wherein the cryogenic media is liquid hydrogen.
 9. The method according to claim 7, wherein the step of forcing the compressed cryogenic media out of the cylinder through the compression valve disposed in the cylinder side wall includes the step of discharging the compressed cryogenic media from a dead space containing the cryogenic media in a gas form through the compression valve.
 10. The method according to claim 7, wherein when the piston is at the lowest-most position in the cylinder, a head of the piston is located adjacent to the compression valve.
 11. The method according to claim 7, wherein a head of the piston has a conical portion.
 12. The method according to claim 11, wherein when the piston is at the lowest-most position in the cylinder, the conical portion of the piston head is located adjacent to the compression valve.
 13. The method according to claim 7, further comprising the step of reducing an amount of gas present in the cylinder by the step of forcing the compressed cryogenic media out of the cylinder through the compression valve disposed in the cylinder side wall.
 14. The method according to claim 12, wherein when the piston is at the lowest-most position in the cylinder, a quantity of compressed cryogenic media in a liquid form remains at the bottom wall of the cylinder. 